#include <iostream>
using namespace std;

const double eps = 1e-8;



int main(){
    double n;
    scanf("%lf", &n);
    double l = -100, r = 100;
    while (r - l > eps){
        double mid = (l + r) / 2;
        //中值的三次方
        if(mid * mid * mid >= n) r = mid ;
        else l = mid;
    }

    printf("%.6lf", l);

    return 0;

}